rhizomania

Rhizomania is a viral disease of sugar beet (Beta vulgaris) and related crops, characterized by excessive proliferation of the root system caused by infection with Beet necrotic yellow vein virus (BNYVV). The disease can lead to severe yield and sugar-quality losses.

Causative agent and transmission are central to rhizomania. Beet necrotic yellow vein virus is a multipartite RNA virus from the family Benyviridae. In many strains, multiple RNA segments (notably RNA1–RNA4, with RNA5 in some virulent forms) influence symptom severity. The virus is transmitted in soil by the plasmodiophorid Polymyxa betae, which forms resting spores that can persist in soil for extended periods and release infectious particles when new sugar beet roots are established.

Symptoms and impact on plants. The hallmark of rhizomania is abnormal root proliferation, producing a dense, fibrous, crown-root system that resembles a root mass “mania.” This root alteration is accompanied by stunting, reduced vigor, and often yellowing or decline in foliage. Plant productivity declines as both root mass and sugar accumulation are compromised, leading to significant yield and quality losses.

Diagnosis and management. Diagnosis relies on symptom observation in the field supported by laboratory detection of BNYVV in roots or soil (serological methods or molecular assays such as RT-PCR). Management emphasizes resistant cultivars carrying appropriate resistance genes, crop rotations with non-host crops, use of clean seed or virus-free planting material, and strategies to limit soil inoculum. Long-term control is challenging due to the persistence of the soil-borne pathogen and the emergence of virulent viral strains.

Global significance. Rhizomania affects major sugar beet-growing regions worldwide and remains a key constraint on production, with ongoing research into resistance and integrated disease management strategies.